The Gateway PRO for wireless multi-zone temperature regulation with built-in GSM, UMTS or LTE modem requires the use of a micro SIM compliant with the GSM 11.12 phase 2+ standard (excluding USIM). It must have an active internet contract (minimum monthly data traffic of 500 MB for each Gateway), either pay as you go or with contract, and the PIN code must be disabled. Please note that a stable mobile phone signal is necessary for the system to function properly, so make sure you choose a suitable telephone service provider.